Silicon single-photon avalanche diodes with nano-structured light trapping

Kai Zang,Xiao Jiang,James S Harris,Matthew Morea,Qiang Zhang,Jian Ma,Ching-Ying Lu,Yijie Huo,Xiaochi Chen,Xun Ding,Ming Zhou,Theodore I Kamins,Zhenyang Xia,Zongfu Yu

doi:10.1038/s41467-017-00733-y

Abstract

Silicon single-photon avalanche detectors are becoming increasingly significant in research and in practical applications due to their high signal-to-noise ratio, complementary metal oxide semiconductor compatibility, room temperature operation, and cost-effectiveness. However, there is a trade-off in current silicon single-photon avalanche detectors, especially in the near infrared regime. Thick-junction devices have decent photon detection efficiency but poor timing jitter, while thin-junction devices have good timing jitter but poor efficiency. Here, we demonstrate a light-trapping, thin-junction Si single-photon avalanche diode that breaks this trade-off, by diffracting the incident photons into the horizontal waveguide mode, thus significantly increasing the absorption length. The photon detection efficiency has a 2.5-fold improvement in the near infrared regime, while the timing jitter remains 25 ps. The result provides a practical and complementary metal oxide semiconductor compatible method to improve the performance of single-photon avalanche detectors, image sensor arrays, and silicon photomultipliers over a broad spectral range.

Highlights

Silicon single-photon avalanche detectors are becoming increasingly significant in research and in practical applications due to their high signal-to-noise ratio, complementary metal oxide semiconductor compatibility, room temperature operation, and cost-effectiveness
To determine if nano-structures affect the dark count rate (DCR) at a lower level, we reduced the DCR by two orders of magnitude through fabricating thicker-junction SPADs, both nano-structured and control devices, on a Si substrate, without the light trapping effect
Given better passivation for surface nanostructures, the dead time and afterpulsing will remain small compared to thick-junction SPADs

Summary

Introduction

Silicon single-photon avalanche detectors are becoming increasingly significant in research and in practical applications due to their high signal-to-noise ratio, complementary metal oxide semiconductor compatibility, room temperature operation, and cost-effectiveness. We demonstrate a light-trapping, thin-junction Si single-photon avalanche diode that breaks this trade-off, by diffracting the incident photons into the horizontal waveguide mode, significantly increasing the absorption length. The peak PDE for a thin-junction SPAD is around 50% at 550 nm, while the typical PDE for a thick-junction SPAD is around 70% at 650 nm[8, 13] In all these applications, near-infrared wavelengths are often used to take advantage of fiber compatibility, eye-safety, and low absorption in solutions. Compared to previous works where PDE follows a 1 − e−αL or 1 − e−2αL relationship with the device layer thickness L and absorption coefficient α, our design diffracts the vertically incident photons into a horizontal waveguide mode, and traps the photons in the thin-film to enhance PDE while keeping a low timing jitter[22]

Methods

Results

Conclusion